I know it may be surprising for someone like me to have been terrified of clowns as a child. Looking back, I'm sure this is one of the largest reasons why. Tim Curry is in my top five favorite actors of all time and for good reason. He caused me to have to go to therapy as a kid for his role in this movie. I had nightmares that turned into daydreams...and eventually called 911 because I knew I saw Pennywise in my house! (I was six, give me a break) Even now I cringe when he says his famous "They all float" line in this movie. No amount of anti-anxiety meds and counseling sessions can erase that for me.
This is one I don't think I will be showing to my own children for years to come. I haven't been able to watch it in it's entirety in twenty years. When looking for terror...this one is it for me.